Effective and reliable adhesive bonds between metal surfaces and rubber substrates are extremely important in automotive and industrial applications which utilize metal components bonded to rubber or elastomer substrates. Various technologies have been previously developed in an attempt to provide an effective rubber-metal bond which will withstand the various conditions encountered in these commercial applications. For example, U.S. Pat. No. 2,581,920 discloses the use of polymers of dichlorobutadiene and chlorinated rubber in rubber-metal adhesives. In addition, U.S. Pat. No. 2,900,292 discusses the bonding of rubber to metal with brominated 2,3-dichlorobutadiene-1,3 polymer. The adhesive composition may optionally contain a material that adheres to metal surfaces such as a thermosetting phenol-aldehyde resin or a halogenated rubber.
U.S. Pat. Nos. 3,258,388 and 3,258,389 disclose an adhesive composition containing a rubber adherent and a metal adherent such that the adhesive will bond metal to rubber upon heating under pressure. Various metal adherents include thermosetting phenol-aldehyde resins, polymers of ethylenically unsaturated materials, halogenated rubber such as chlorinated natural rubber or chlorinated polychloroprene. The rubber adherent basically consists of a poly-C-nitroso compound although various other rubber adhering components may be utilized such as vulcanizable olefins.
U.S. Pat. No. 4,769,413 discloses a metal coating composition which may be utilized as a primer in rubber-metal bonding. The composition consists of a blocked isocyanate-functional urethane prepolymer, a phenolic resin, and a halogenated resin such as halogenated rubber dispersed in an inert solvent.
Recent technological advances in automotive and industrial applications have resulted in relatively severe working environments for adhesively bonded rubber and metal components. For example, many fluid-filled engine mounts are being exposed to increasingly high temperatures such that the rubber-metal bond on the mount is exposed to very high temperature fluid environments. Furthermore, many adhesively bonded components are crimped or squeezed into desired shapes or configurations prior to use in a final application.
It has been found that many of the above adhesive systems containing halogenated rubbers such as chlorinated natural rubber cannot withstand the harsh conditions imposed by these environments. For example, in high temperature environments, many of the traditional rubber-metal bonding compositions will blister or rapidly corrode. In addition, the relatively brittle rubber-metal bonds formed from traditional compositions cannot withstand the crimping or squeezing required in many applications. A need therefore exists for a rubber-metal adhesive system which will withstand these increasingly demanding conditions.